source-code.md: Update latest stable version
source-code.md: Update latest stable version

Update the latest stable version to Dab 4.0.2.

Bug-AGL: SPEC-1024

Signed-off-by: Leon Anavi <15d13d7e2c6115f28df053122512bfcb5eb2dbf7@konsulko.com>

automotive-grade-linux/docs-agl,leon-anavi/docs-agl,leon-anavi/docs-agl,leon-anavi/docs-agl,claneys/docs-agl,claneys/docs-agl,automotive-grade-linux/docs-agl,claneys/docs-agl,claneys/docs-agl,automotive-grade-linux/docs-agl,leon-anavi/docs-agl,automotive-grade-linux/docs-agl